阅读说明：本技术 一种生物基阻燃剂的制备方法及制备阻燃聚氨酯泡沫的方法 (Preparation method of bio-based flame retardant and method for preparing flame-retardant polyurethane foam ) 是由 高明 李永鹏 岳丽娜 李勇军 周旋 于 2020-07-03 设计创作，主要内容包括：本发明公开了一种生物基阻燃剂的制备方法,包括以下操作步骤；(1)向植酸水溶液中加入蒸馏水稀释后,向其中持续缓慢加入碳酸钠粉末,搅拌均匀后,直至体系的pH值为6.5-7.2后,停止加入碳酸钠粉末,得到植酸钠水溶液；(2)将单宁酸水溶液和乙二醇按照体积比为3-4:1的比例混合均匀后,再向其中加入植酸钠水溶液和浓硫酸水溶液后,油浴下升温至40-50℃后,反应时间3-4h,抽滤,用蒸馏水反复洗涤滤饼3次,收集白色固体干燥后得单宁植酸酯。本发明制得的生物基阻燃剂阻燃性能优异,并且对聚氨酯泡沫的力学性能影响较少,能使得聚氨酯泡沫的力学性能和阻燃性能达到平衡。(The invention discloses a preparation method of a bio-based flame retardant, which comprises the following operation steps; (1) adding distilled water into the phytic acid aqueous solution for dilution, continuously and slowly adding sodium carbonate powder into the phytic acid aqueous solution, uniformly stirring the solution until the pH value of the system is 6.5-7.2, and stopping adding the sodium carbonate powder to obtain the sodium phytate aqueous solution; (2) uniformly mixing a tannic acid aqueous solution and ethylene glycol according to a volume ratio of 3-4:1, adding a sodium phytate aqueous solution and a concentrated sulfuric acid aqueous solution, heating to 40-50 ℃ under an oil bath, reacting for 3-4h, performing suction filtration, repeatedly washing a filter cake for 3 times by using distilled water, collecting a white solid, and drying to obtain the tannic phytate. The prepared bio-based flame retardant has excellent flame retardant property, has little influence on the mechanical property of polyurethane foam, and can balance the mechanical property and the flame retardant property of the polyurethane foam.)

1. The preparation method of the bio-based flame retardant is characterized by comprising the following operation steps;

(1) adding distilled water into the phytic acid aqueous solution for dilution, continuously and slowly adding sodium carbonate powder into the phytic acid aqueous solution, uniformly stirring the solution until the pH value of the system is 6.5-7.2, and stopping adding the sodium carbonate powder to obtain the sodium phytate aqueous solution;

(2) uniformly mixing a tannic acid aqueous solution and ethylene glycol according to a volume ratio of 3-4:1, adding a sodium phytate aqueous solution and a concentrated sulfuric acid aqueous solution, heating to 40-50 ℃ under an oil bath, reacting for 3-4h, performing suction filtration, repeatedly washing a filter cake for 3 times by using distilled water, collecting a white solid, and drying to obtain the tannic phytate.

2. The method for preparing a bio-based flame retardant according to claim 1, wherein in the step (1), the volume ratio of the phytic acid aqueous solution to the distilled water is 8-12:5, and the mass fraction of the phytic acid aqueous solution is 65-75%.

3. The method of claim 1, wherein the aqueous solution of tannic acid in step (2) is 4-6 wt%.

4. The preparation method of the bio-based flame retardant according to claim 1, wherein in the step (2), the volume ratio of the sodium phytate aqueous solution to the tannin aqueous solution is 3-5:4, the mass fraction of the concentrated sulfuric acid aqueous solution is 98%, and the volume ratio of the concentrated sulfuric acid aqueous solution to the ethylene glycol is 5-7: 1.

5. A process for the preparation of flame retarded polyurethane foams based on flame retardants according to any of claims 1 to 4, characterized in that it comprises the following operative steps:

(1) paraformaldehyde, ethylene glycol, melamine and urea are mixed according to the mass ratio of 1.0 (1.5-2.5) to 3.0-3.5: (0.5-1.5), raising the temperature of the mixture to 110 ℃, keeping the temperature for reaction for 25-30min, adding ammonium chloride, adjusting the pH value of the system to 4.0-4.5, continuing to react for 25-30min, adding diethanolamine, adjusting the pH value of the system to 9.0-9.5, continuing to perform curing reaction at 75-85 ℃ for 50-70min to obtain ethylene glycol modified melamine resin;

(2) adding tannin phytate into the ethylene glycol modified melamine resin prepared in the step (1), mixing and stirring uniformly, and reacting for 0.5-1h at 20-40 ℃ to prepare the bio-based macromolecular intumescent flame retardant;

(3) according to the weight portion, after 35 to 45 portions of polyvinyl alcohol LY-403 and 55 to 65 portions of ethylenediamine rigid foam polyether polyol LCN-405 are mixed, continuously stirred and reacted for 120min, then 0.8-1.2 parts of foam stabilizer AK-8850, 0.09-0.10 parts of diethanolamine, 0.09-0.10 parts of epoxy compound TEDA and 1-3 parts of deionized water are added into the mixture, then the mixture is stirred and reacted for 110-120 seconds, adding 85-95 parts of polymethylene polyphenyl polyisocyanate, stirring and reacting for 9-11 seconds at the rotating speed of 1800-2200r/min, pouring out for free foaming, curing to obtain flame-retardant polyurethane foam, wherein the weight part of the glycol modified melamine resin used for preparing the bio-based macromolecular intumescent flame retardant is 50 parts.

6. The method for preparing flame retardant polyurethane foam according to claim 5, wherein in the step (2), the mass ratio of the glycol-modified melamine resin to the tannin phytate is 5: 1-2.

7. The method for preparing flame retardant polyurethane foam of claim 5, wherein in the step (3), the curing conditions are as follows: the curing temperature is 65-75 ℃, and the curing time is 34-38 hours.

Technical Field

The invention relates to the technical field of preparation of flame-retardant materials, in particular to a preparation method of a bio-based flame retardant and a method for preparing flame-retardant polyurethane foam.

Background

Polyurethane foams (PUFs) are polymeric materials containing repeating urethane linkages in the molecular chain, formed by the polyaddition of molecules containing two or more isocyanate functional groups with polyols containing two or more reactive hydroxyl groups in suitable proportions and in the presence of a suitable catalyst. Polyurethanes can be classified into two major categories, namely hard and soft, and have many advantages such as excellent flexibility, mechanical strength, wear resistance and weather resistance, and therefore, they are very important in the new material industry. The soft polyurethane mainly has a thermoplastic linear structure, has the excellent characteristics of light weight, good elasticity, low price and the like, and is widely used for materials of furniture, sound insulation, shock resistance, filtration and the like. The hard polyurethane foam has intramolecular cross-linking, high strength and insolubility, and is used mainly in building, household appliance, automobile, aviation and heat insulating material. In the life of people, the demand of polyurethane plastics is increasing from the viewpoint of the wide application of synthetic resins, and only the demand is increasing with general-purpose plastics such as polyethylene and polypropylene. Since the industrialization of China, the technology in the synthesis and flame retardant of polyurethane is also increasing.

However, polyurethane foam, as a foam material, contains a flammable hydrogen bond segment therein, and has the characteristics of low density, large specific area and the like. Polyurethane is a flammable organic polymer material, the polyurethane material which is not subjected to flame retardant treatment is extremely easy to burn when meeting fire, the Limiting Oxygen Index (LOI) of the polyurethane material is generally about 18 percent, and when the polyurethane material is burnt when meeting fire, the contact area of a cell structure and oxygen is large, and a large amount of toxic smog is generated. With the improvement of the quality of life of people, the development of flame retardant materials has become the focus of attention of experts and scholars, and good progress is made. The currently commonly used flame retardants are mainly classified into halogen-containing flame retardants, organic and inorganic phosphorus flame retardants, intumescent flame retardants, nitrogen-containing flame retardants, inorganic nanofillers, and the like. Halogen-containing flame retardants are among the most productive organic flame retardants today. The halogen flame retardant has high flame retardant efficiency and low price, and has better performance and price than other flame retardants. The halogen flame retardant is often used in the building and electronic industries, and the market demand is large, about 60-90. And because the halogen-containing flame retardant has various varieties and wide application range, the halogen-containing flame retardant is always the first choice of people. Bromine-based flame retardants are used for a relatively long period of time and continue to be used without suitable substitutes for bromine-based flame retardants. However, the absence of halogen elements in flame retardants is a final goal in the long run. The application of the phosphorus-containing flame retardant comprises the following steps: can be used as fire retardant for adhesives, coatings, thermosetting plastics, thermoplastic plastics, paper and the like. The main types are red phosphorus, insoluble ammonium polyphosphate, organic phosphate, water-soluble inorganic phosphate and the like. The mechanism of Intumescent Flame Retardants (IFR) is condensed phase flame retardance. The acid source, the carbon source and the gas source form the intumescent flame retardant. The formation process of the intumescent flame retardant porous carbon layer is shown in figure 1.

Under the action of three components of the intumescent flame retardant, an acid source can release inorganic acid to promote esterification of carbon source polyhydric alcohol, the carbon source polyhydric alcohol is used as a dehydrating agent, the dehydrating agent and the carbon source are subjected to esterification reaction, a catalyst amine accelerates the esterification reaction, and the gas generated in the combustion process of the gas source and the system expands and foams a molten system, so that a porous foam carbon layer is generated by solidification.

TABLE 1 IFR major Components

With the exposure of the problems of secondary pollution and excessive consumption of non-renewable energy resources, the traditional flame-retardant polyurethane foams such as halogen flame retardants cannot meet the concept of green environmental protection, and the intumescent flame retardants taking bio-based as raw materials attract attention of people. Most of the biobase is derived from each organ of plants, and has excellent performances of being reproducible, degradable and the like. However, the existing intumescent flame retardant taking the bio-based as the raw material has poor flame retardant property, the addition amount of the intumescent flame retardant in polyurethane foam is small, excellent flame retardant effect cannot be achieved, and when the addition amount is large, various mechanical properties of the polyurethane foam can be seriously influenced, so that the application of the intumescent flame retardant taking the bio-based as the raw material in the field of polyurethane foam is seriously limited.

Disclosure of Invention

In order to solve the existing problems, the invention provides a preparation method of a bio-based flame retardant and a method for preparing flame-retardant polyurethane foam.

The invention is realized by the following technical scheme:

a preparation method of a bio-based flame retardant comprises the following operation steps;

(1) adding distilled water into the phytic acid aqueous solution for dilution, continuously and slowly adding sodium carbonate powder into the phytic acid aqueous solution, uniformly stirring the solution until the pH value of the system is 6.5-7.2, and stopping adding the sodium carbonate powder to obtain the sodium phytate aqueous solution;

(2) uniformly mixing a tannic acid aqueous solution and ethylene glycol according to a volume ratio of 3-4:1, adding a sodium phytate aqueous solution and a concentrated sulfuric acid aqueous solution, heating to 40-50 ℃ under an oil bath, reacting for 3-4h, performing suction filtration, repeatedly washing a filter cake for 3 times by using distilled water, collecting a white solid, and drying to obtain tannin phytate, which is called TAP for short.

Specifically, in the step (1), the volume ratio of the phytic acid aqueous solution to the distilled water is 8-12:5, and the mass fraction of the phytic acid aqueous solution is 65-75%.

Specifically, in the step (2), the mass fraction of the aqueous solution of tannic acid is 4-6%.

Specifically, in the step (2), the volume ratio of the sodium phytate aqueous solution to the tannin aqueous solution is 3-5:4, the mass fraction of the concentrated sulfuric acid aqueous solution is 98%, and the volume ratio of the concentrated sulfuric acid aqueous solution to the ethylene glycol is 5-7: 1.

The invention also provides a method for preparing flame-retardant polyurethane foam by using the bio-based flame retardant, which comprises the following operation steps:

(1) paraformaldehyde, ethylene glycol, melamine and urea are mixed according to the mass ratio of 1.0 (1.5-2.5) to 3.0-3.5: (0.5-1.5), heating the mixture to 110 ℃, keeping the temperature for reaction for 25-30min, adding ammonium chloride, adjusting the pH value of the system to 4.0-4.5, continuing to react for 25-30min, adding diethanolamine, adjusting the pH value of the system to 9.0-9.5, continuing to cure and react for 50-70min at 75-85 ℃, and obtaining ethylene glycol modified melamine resin, EMF resin for short;

(2) adding tannin phytate into the ethylene glycol modified melamine resin prepared in the step (1), mixing and stirring uniformly, and reacting for 0.5-1h at 20-40 ℃ to prepare a bio-based macromolecular intumescent flame retardant, TAPM for short;

(3) according to the weight portion, after 35 to 45 portions of polyvinyl alcohol LY-403 and 55 to 65 portions of ethylenediamine rigid foam polyether polyol LCN-405 are mixed, continuously stirred and reacted for 120min, then 0.8-1.2 parts of foam stabilizer AK-8850, 0.09-0.10 parts of diethanolamine, 0.09-0.10 parts of epoxy compound TEDA and 1-3 parts of deionized water are added into the mixture, then the mixture is stirred and reacted for 110-120 seconds, 85-95 parts of polymethylene polyphenyl polyisocyanate is added into the mixture, the rotation speed of 1800-2200r/min is adopted, after the stirring reaction is carried out for 9-11 seconds, pouring out, freely foaming, curing to obtain flame-retardant polyurethane foam, RPUF for short, wherein the weight part of the glycol modified melamine resin used for preparing the bio-based macromolecular intumescent flame retardant is 50 parts.

Specifically, in the step (2), the mass ratio of the ethylene glycol modified melamine resin to the tannin phytate is 5: 1-2.

Specifically, in the step (3), the curing conditions are as follows: the curing temperature is 65-75 ℃, and the curing time is 34-38 hours.

According to the technical scheme, the beneficial effects of the invention are as follows:

the prepared bio-based flame retardant has excellent flame retardant property, can form a compact carbon layer after combustion, effectively blocks heat transfer, provides a good protective layer for polyurethane foam, and can ensure that the flame retardant property of the polyurethane foam reaches V-0 level only by adding a small amount of the bio-based flame retardant; the bio-based flame retardant prepared by the invention has little influence on the mechanical property of polyurethane foam, and can balance the mechanical property and the flame retardant property of the polyurethane foam.

Drawings

FIG. 1 is a schematic view of a process for forming a porous carbon layer of an intumescent flame retardant.

FIG. 2 shows EMF¹³C-NMR spectrum.

FIG. 3 is a thermogravimetric plot of a polyurethane foam sample.

FIG. 4 is a differential thermogravimetric plot of a polyurethane foam sample.

FIG. 5 is a graph of the heat release rate of a sample of polyurethane foam.

FIG. 6 is a graph of the total heat released for a polyurethane foam sample.

Fig. 7 is an SEM image of the polyurethane foam sample residue after cone calorimetry: (a) RPUF-1, (b) RPUF-2, (c) RPUF-3 and (d) RPUF-4.

FIG. 8 is a transmission electron micrograph of a polyurethane foam sample: RPUF-1 (left) and RPUF-4 (right).

Detailed Description

Embodiments of the present invention will be described in detail below with reference to examples, but it will be understood by those skilled in the art that the following examples are only illustrative of the present invention and should not be construed as limiting the scope of the present invention. The examples, in which specific conditions are not specified, were conducted under conventional conditions or conditions recommended by the manufacturer. The reagents or instruments used are not indicated by the manufacturer, and are all conventional products available commercially.